Many voltage detecting circuits have heretofore been proposed. For example, there is a circuit system which obtains a divided voltage by means of resistors and detects this divided voltage with an inverter and a display circuit which is driven by the variation of the output voltage of the inverter. However, since this circuit system is always in operation, it dissipates the power of the power source.
In order to overcome this defect, an intermittent circuit has been proposed. In this case, there is provided a voltage detecting circuit, the output signal of which becomes logic level "1" when the output signal is above a predetermined voltage level and becomes logic level "0" when the output signal is below the predetermined voltage level. Accordingly, this voltage detecting circuit detects only high voltage or low voltage.